This invention relates generally to the field of combustion turbine engines and more particularly, to the recovery of water from the exhaust of a combustion turbine engine.
Water or steam injection can be used for power augmentation and/or the control of nitrous oxide emissions in a combustion turbine powered electrical generating plant. The cost of the water used in this process can be significant, and it is becoming increasingly difficult in some areas to obtain a permit to use water for power generation. Accordingly, it is desirable to recover water from the exhaust stream of a combustion turbine.
Water is a natural byproduct of the combustion of hydrocarbon fuels. It is known that cooling the exhaust stream from a combustion turbine in a condenser to below the precipitation temperature of the moisture in the exhaust gas will result in the condensation of a portion of the moisture contained in the exhaust gas. The quantity and percentage of the moisture recovered is a function of the temperature to which the exhaust can be cooled by the condenser. Ambient air is commonly the ultimate heat sink for such condensers, and the ambient air temperature thus determines the amount of moisture that can be removed by the condenser. In an arid desert environment, where it is most likely that water recovery will be desired, the daytime ambient air temperature may be over 100xc2x0 F. or even 110xc2x0 F. and the effectiveness of water removal by an air-cooled condenser is limited.
It is known that sulfur contained in the fossil fuel burned in a combustion turbine will result in the presence of sulfuric acid in the combustion turbine exhaust stream. While the concentration of sulfur may be relatively low, the sulfur will condense from the exhaust gas stream at a slightly higher temperature than the temperature at which water will condense, and thus a locally high concentration of sulfuric acid may develop on portions of the tubes of the condenser. Sulfuric acid is very corrosive to the carbon steels that are normally used to manufacture condenser tubes, and thus stainless steel, having a higher cost, must be used.
U.S. Pat. No. 5,843,214 describes a system for capturing a condensable vapor such as water in a combustion turbine exhaust stream. This system uses a fog of water particles to cause moisture in the combustion turbine exhaust to condense to form a warm rain of condensate. The patent illustrates the condensate being cooled using seawater as the ultimate heat sink. Seawater may be sufficiently cold to provide an adequate level of moisture removal from the combustion turbine exhaust; however, such a system would be far less efficient in a high temperature desert environment where only air-cooled condensate is available.
Accordingly, an improved system for recovering water from a combustion turbine exhaust stream containing sulfuric acid is needed for use at locations where an adequately cold ultimate heat sink is not available.
A power plant is described herein as including: a combustion turbine engine receiving fuel and air and producing shaft power and exhaust gas; and a water stripper receiving the exhaust gas, the water stripper comprising a desiccant. The power plant may further include a sulfur stripper disposed in a flow path of the exhaust gas between the combustion turbine engine and the water stripper. The sulfur stripper may be a water contact heat exchanger including a media for providing surface area contact between the exhaust gas and a flow of water. A fluid connection may be included for providing water removed from the exhaust gas by the water stripper to the water contact heat exchanger. The power plant may further include a sub-atmospheric regenerator receiving a first concentration of the aqueous solution of the desiccant from the absorber and producing steam and a second concentration of the aqueous solution of the desiccant dryer than the first concentration.
A power plant is described herein as including: a combustion turbine for receiving fuel and air and for producing shaft power and exhaust gas; a sulfur stripper receiving the exhaust gas from the combustion turbine, the sulfur stripper providing surface area contact between the exhaust gas and a flow of water, a portion of the flow of water evaporating into the exhaust gas and sulfur from the exhaust gas condensing into the flow of water; and a heat exchanger receiving the exhaust gas from the sulfur stripper and removing water from the exhaust gas. The heat exchanger may be a direct contact heat exchanger providing surface area contact between the exhaust gas and an aqueous solution of a desiccant. The power plant may further include: a sub-atmospheric regenerator receiving the aqueous solution of the desiccant from the direct contact heat exchanger; and a condenser in fluid communication with the sub-atmospheric pressure and maintaining a sub-atmospheric pressure in the sub-atmospheric regenerator to produce steam from the aqueous solution of the desiccant.
A water recovery apparatus for use with a combustion turbine engine is described herein as including: a sulfur stripper for removing sulfur from a stream of combustion turbine exhaust gas; and an absorber comprising a desiccant disposed in the stream of combustion turbine exhaust gas downstream of the sulfur stripper for chemically absorbing water from the exhaust gas.
A water recovery apparatus for use with a combustion turbine engine is also described as including: a sulfur stripper for receiving the exhaust gas from a combustion turbine, the sulfur stripper comprising a fill material for providing surface area contact between the exhaust gas and a flow of water for cooling the exhaust gas by evaporating a portion of the flow of water to add moisture to the exhaust gas and to remove sulfur from the exhaust gas into the flow of water; and a water stripper disposed in the exhaust gas downstream of the sulfur stripper for removing water from the exhaust gas.
A method of recovering water from the exhaust of a combustion turbine engine is described herein as including: exposing sulfur-containing exhaust gas from a combustion turbine engine to a flow of water to cool the sulfur-containing exhaust gas to a temperature below a precipitation temperature of sulfur to precipitate sulfur into the flow of water to produce a substantially sulfur-free exhaust gas; and directing the substantially sulfur-free exhaust gas to a water stripper to recover water from the exhaust gas. The method may include exposing the substantially sulfur-free exhaust gas to an aqueous solution of a desiccant to absorb water from the exhaust gas. The method may further include reducing pressure on the aqueous solution of a desiccant to produce steam to remove water absorbed from the exhaust gas.